SCGSKELETON(1L) Schily´s USER COMMANDS SCGSKELETON(1L)NAMEscgskeleton - Skeleton program for SCSI transport using libscg
SYNOPSISscgskeleton dev=device [ options ]
DESCRIPTION
Scgskeleton is s skeleton program to demonstrate the interfaces and
capabilities of the SCSI transport library libscg.
Device naming
For a list of possible device name parameters call scgskeleton-scanbus
or scgskeleton dev=help and then use the right dev= parameter based on
the device listing.
OPTIONS-help Prints a short summary of the p options and exists.
-version
Print version information and exit.
dev=target
Set the SCSI target for the CD/DVD/BluRay-Recorder, see notes
above. A typical target device specification is dev=1,6,0 . If
a filename must be provided together with the numerical target
specification, the filename is implementation specific. The
correct filename in this case can be found in the system spe‐
cific manuals of the target operating system. On a FreeBSD sys‐
tem without CAM support, you need to use the control device
(e.g. /dev/rcd0.ctl). A correct device specification in this
case may be dev=/dev/rcd0.ctl:@ .
General SCSI addressing
The target device to the dev= option refers to scsibus/tar‐
get/lun of the CD/DVD/BluRay-Recorder. Communication on SunOS is
done with the SCSI general driver scg. Other operating systems
are using a library simulation of this driver. Possible syntax
is: dev= scsibus,target,lun or dev= target,lun. In the latter
case, the CD/DVD/BluRay-Recorder has to be connected to the
default SCSI bus of the machine. Scsibus, target and lun are
integer numbers. Some operating systems or SCSI transport
implementations may require to specify a filename in addition.
In this case the correct syntax for the device is: dev= device‐
name:scsibus,target,lun or dev= devicename:target,lun. If the
name of the device node that has been specified on such a system
refers to exactly one SCSI device, a shorthand in the form dev=
devicename:@ or dev= devicename:@,lun may be used instead of
dev= devicename:scsibus,target,lun.
Remote SCSI addressing
To access remote SCSI devices, you need to prepend the SCSI
device name by a remote device indicator. The remote device
indicator is either REMOTE:user@host: or REMOTE:host: A valid
remote SCSI device name may be: REMOTE:user@host: to allow
remote SCSI bus scanning or REMOTE:user@host:1,0,0 to access the
SCSI device at host connected to SCSI bus # 1,target 0, lun 0.
In order to allow remote access to a specific host, the rscsi(1)
program needs to be present and configured on the host.
Alternate SCSI transports
ATAPI drives are just SCSI drives that inherently use the ATA
packet interface as SCSI command transport layer build into the
IDE (ATA) transport. You may need to specify an alternate
transport layer on the command line if your OS does not imple‐
ment a fully integrated kernel driver subsystem that allows to
access any drive using SCSI commands via a single unique user
interface.
To access SCSI devices via alternate transport layers, you need
to prepend the SCSI device name by a transport layer indicator.
The transport layer indicator may be something like USCSI: or
ATAPI:. To get a list of supported transport layers for your
platform, use dev= HELP:
Portability Background
To make scgskeleton portable to all UNIX platforms, the syntax
dev= devicename:scsibus,target,lun is preferred as it hides OS
specific knowledge about device names from the user. A specific
OS may not necessarily support a way to specify a real device
file name nor a way to specify scsibus,target,lun.
Scsibus 0 is the default SCSI bus on the machine. Watch the boot
messages for more information or look into /var/adm/messages for
more information about the SCSI configuration of your machine.
If you have problems to figure out what values for scsibus,tar‐
get,lun should be used, try the -scanbus option of scgskeleton
described below.
Using logical names for devices
If no dev option is present, scgskeleton will try to get the
device from the CDR_DEVICE environment.
If a file /etc/default/cdrecord exists, and if the argument to
the dev= option or the CDR_DEVICE environment does not contain
the characters ',', '/', '@' or ':', it is interpreted as a
device label name that was defined in the file
/etc/default/cdrecord (see FILES section).
Autotarget Mode
If no dev= option and no CDR_DEVICE environment is present, or
if it only contains a transport specifyer but no address nota‐
tion, scgskeleton tries to scan the SCSI address space for CD-
ROM drives. If exactly one is found, this is used by default.
timeout=#
Set the default SCSI command timeout value to # seconds. The
default SCSI command timeout is the minimum timeout used for
sending SCSI commands. If a SCSI command fails due to a time‐
out, you may try to raise the default SCSI command timeout above
the timeout value of the failed command. If the command runs
correctly with a raised command timeout, please report the bet‐
ter timeout value and the corresponding command to the author of
the program. If no timeout option is present, a default timeout
of 40 seconds is used.
debug=#, -d
Set the misc debug value to # (with debug=#) or increment the
misc debug level by one (with -d). If you specify -dd, this
equals to debug=2. This may help to find problems while opening
a driver for libscg. as well as with sector sizes and sector
types. Using -debug slows down the process and may be the rea‐
son for a buffer underrun.
kdebug=#, kd=#
Tell the scg-driver to modify the kernel debug value while SCSI
commands are running.
-silent, -s
Do not print out a status report for failed SCSI commands.
-v Increment the level of general verbosity by one. This is used
e.g. to display the progress of the process.
-V Increment the verbose level with respect of SCSI command trans‐
port by one. This helps to debug problems during the process,
that occur in the CD-Recorder. If you get incomprehensible
error messages you should use this flag to get more detailed
output. -VV will show data buffer content in addition. Using
-V or -VV slows down the process. -scanbus Scan all SCSI
devices on all SCSI busses and print the inquiry strings. This
option may be used to find SCSI address of the devices on a sys‐
tem. The numbers printed out as labels are computed by: bus *
100 + target
ts=# Set the maximum transfer size for a single SCSI command to #.
The syntax for the ts= option is the same as for cdrecord fs=#
or sdd bs=#.
If no ts= option has been specified, scgskeleton defaults to a
transfer size of 256 kB. If libscg gets lower values from the
operating system, the value is reduced to the maximum value that
is possible with the current operating system. Sometimes, it
may help to further reduce the transfer size or to enhance it,
but note that it may take a long time to find a better value by
experimenting with the ts= option.
EXAMPLESENVIRONMENT
RSH If the RSH environment is present, the remote connection will
not be created via rcmd(3) but by calling the program pointed to
by RSH. Use e.g. RSH=/usr/bin/ssh to create a secure shell
connection.
Note that this forces cdrecord to create a pipe to the rsh(1)
program and disallows cdrecord to directly access the network
socket to the remote server. This makes it impossible to set up
performance parameters and slows down the connection compared to
a root initiated rcmd(3) connection.
RSCSI If the RSCSI environment is present, the remote SCSI server will
not be the program /opt/schily/sbin/rscsi but the program
pointed to by RSCSI. Note that the remote SCSI server program
name will be ignored if you log in using an account that has
been created with a remote SCSI server program as login shell.
SEE ALSOcdrecord(1), scg(7), rcmd(3), ssh(1).
NOTESDIAGNOSTICS
A typical error message for a SCSI command looks like:
scgskeleton: I/O error. test unit ready: scsi sendcmd: no error
CDB: 00 20 00 00 00 00
status: 0x2 (CHECK CONDITION)
Sense Bytes: 70 00 05 00 00 00 00 0A 00 00 00 00 25 00 00 00 00 00
Sense Key: 0x5 Illegal Request, Segment 0
Sense Code: 0x25 Qual 0x00 (logical unit not supported) Fru 0x0
Sense flags: Blk 0 (not valid)
cmd finished after 0.002s timeout 40s
The first line gives information about the transport of the command.
The text after the first colon gives the error text for the system call
from the view of the kernel. It usually is: I/O error unless other
problems happen. The next words contain a short description for the
SCSI command that fails. The rest of the line tells you if there were
any problems for the transport of the command over the SCSI bus. fatal
error means that it was not possible to transport the command (i.e. no
device present at the requested SCSI address).
The second line prints the SCSI command descriptor block for the failed
command.
The third line gives information on the SCSI status code returned by
the command, if the transport of the command succeeds. This is error
information from the SCSI device.
The fourth line is a hex dump of the auto request sense information for
the command.
The fifth line is the error text for the sense key if available, fol‐
lowed by the segment number that is only valid if the command was a
copy command. If the error message is not directly related to the cur‐
rent command, the text deferred error is appended.
The sixth line is the error text for the sense code and the sense qual‐
ifier if available. If the type of the device is known, the sense data
is decoded from tables in scsierrs.c . The text is followed by the
error value for a field replaceable unit.
The seventh line prints the block number that is related to the failed
command and text for several error flags. The block number may not be
valid.
The eight line reports the timeout set up for this command and the time
that the command really needed to complete.
BUGSAUTHOR
Joerg Schilling
Seestr. 110
D-13353 Berlin
Germany
Additional information can be found on:
http://cdrecord.berlios.de/private/cdrecord.html
If you have support questions, send them to:
cdrecord-support@berlios.de
If you have definitely found a bug, send a mail to:
cdrecord-developers@berlios.de
or joerg.schilling@fokus.fraunhofer.de
To subscribe, use:
http://lists.berlios.de/mailman/listinfo/cdrecord-developers
or http://lists.berlios.de/mailman/listinfo/cdrecord-support
Joerg Schilling 2010/05/13 SCGSKELETON(1L)
